System of electric distribution.



E. F. W. ALEXANDERSON. SYSTEM OF BLEGTRIG DISTRIBUTION.

APPLICATION FILED JAN. 7, 190B.

Patented May 18, 1909.

Fig.3.

Invenar Ernst FTWAiexa derson, y

UNITED STIDXTES PAlllilNT O I ,l l 1l l.

ERNST F. W. ALEXANDERSON, 0F S(Jl ll5Nl+lC'lAl)Y, NEW YORK, ASSIGNOR TO GENERAL ELEUTRH) COMPANY, A C(JRIORA'IIUN OF NEW YOK. K.

Specification of Letters Patent. Application filed January 7, 1908.

Patented May 18, 1909. Serial No. 409,698.

To all whom it may concern:

Be it known that I, ERNST F, ANDERSON, a citizen of the United siding, at Schenectady, tady, State of New York, have invented cer tain new and useful Improvements in Systems of Electric Distribution, of which the following is a specification.

y invention relates to multiple conduc- I tor direct current systems of distribution such as three wire systems, and more parti- 1 cularly to generators for supplying such P systems.

The generators ordinarily used for threewire and similar systems are unsatisfactory for systems which may he unbalanced be cause even a comparatively slight difference in load between the two sides of the system causes the otential on the side havin the greater load to drop very rapidly so that if the difference in load becomes as reat as 25 per cent. the potential on the side loving the greater load becomes too low for satisfactory operation of incandescent lamps. Compounding the generator in the ordinary way does not overcome the difficulty, which is not due to decrease in potential between the ou tside Wires'but results from the otential between the neutral and one outside wire being different from the potential between the neutral and the other outside wire.

My invention consists in providing means for automatieall" compounding the voltage between the neutral and an outside wire with varying load.

M ore specifically stated, my invention consists in providing automatic means for impressing an alternating voltage, increasin with increasing load, upon the neutra which voltage combines with the constant W. ALEX j voltage between the neutral and an outside Wire m such a manner that a resultant pulsating voltage is produced between the neutral and outside wire, the effective value of which is greater than that of the constant voltage alone.

The above described method of compounding the neutral to regr ulate the voltage may be applied to any mu tiple conductor system in a great variety of ways but is preferably i carried out by means of'the generator, in l which as commonly constructed for three- Wire systems, a reactance or compensator connected to points on the armature 180 electrical degrees has a tap at the middle or I conneotim the neutral to the States, recounty of Schenecgenerator. In case the olltcrrmting voltage is derived l'rom the "monitor, my invention conieii'iplates the shifting, either actually or in client, of the point of connection of the neutral the middle of the reectance in proportion to the extent of the enlmlanr-in ol the system until at the limit of unlmlencing the result is the same as though the neutral were corn ncoted to .1 segment or the ronnmitator durlog a complete revolution of the armature.

The alternating 'V'Olllil e impressed on the neutral combines with i e steady voltage of the neutral in (uadrature to produce a pal eating voltage etwecn the neutral and the outside wires varying in amount with the amount of current in the neutral. Since the effective voltage is the square root of the average square of the momentary voltages, the potential between theneutrul and outside wires becomes greater than the normal and compensates for the drop caused by the unbalancin ofthe system. This result may be obtainer? the preferred an'angement two reactanoe coils with separate cores are connected in series across the armature between points 180 electrical degrees apsrtand the neutral is connected to it point between the coils. The two coils have different characteristics, the saturation curve of one being nearly in merry different ways but in straight while the curve of tl'xeother has a sharp bend in it. The coils are so pro yortioncd thet n'nder norma'l conditions, oth hove the same Peactance but es the current in the neutral increases the roacfance of the one coil changes and that of the other remains practically unchanged. When the system is balanced the neutral wire is connected to the neutral point of the armature, while as the system becomes imbalanced. the two eoilscollpemte to cause an effect which is the equivalent of connecting the neutral to a segment of the commutator to cause a pulsating voltage between the neutral and the outside wire on that side of the system carrying the greater load.

s form in which my invention may be embodied is shown in the accompanying drawings in whieh Figure I is a diagram showin and 'tlrree wire system embed 1g one form of my invention;- Figs" 2' an 3 are, curves showing the characteristics of the two reactancc coils shown in Fig. 1; and Figs. 4

7 current.

- the neutral.

in the form of the in vcntion shown in Fig. .l, the generator comprises iiold magnets l and an armature 2 of the usual type having a commutator 3 conncctedto the outside wires 4 and 5 of the system. The neutral on the system is derived by connecting points 7 and 8 on the armature, which are 180 electrical degrees apart, to collector" rings 9 and 10 engaged by brushes 11 and 12 which are connected to each other through two reactaln-e coils 13 and 14 in series with each other. A neutral point 15 exists be tween the two rcactance coils and to this point the neutral wire 16 of the s stem is connected. Vhen the system is )alanccd no current flows in the neutral wire 16, but when the system is unbalanced the excess load, represented by the lamps 17, appears on one side of the system, as for instance between the neutral and the outside wire 5, and causes current in the neutral and also a drop in voltage between the wires, which is compensated by var ing the voltage on the neutral, preferably y deriving an alter natingwoltage from the armature 2 and superposing it on the steady voltage of the neutral in such a way that the effective voltage between the neutral and the outside wires is varied. in the arrangement shown in the drawing, the two reactanrc coils con stitute a device which will vary automatically the eii'ective voltage between the neutral and the outside wires to the same extent as the current between those wires varies, if the reactance between the points 7 and S is made to vary in response to the current. An automatic variation of the reactancc, in response to current, is secured in the specific arrangement shown in the drawings by roportioning the coils to have different c aracteristics and connecting them in series be tween the points 7 and 8 with the neutral wire connected to a point between the coils.

The coils are preferably so proportioned that the core of coil 13 ecoines saturated with a current which is only a small fraction of the current re uired to saturate the core of the coil 14. T e characteristic of the coil 13, as shown in Fig. 2, has a sharp bend in it, while that of coil 14 as shown in Fig. 3 is practically a straight line. The reactance of the coils varies une ually with the same variations in current ecause the reactancc of coil 13 becomes ractically constant as soon as the current '6 irough it reaches the small amount required to saturate its core, while the reactance 0% coil 14 increases with the The e ect of this arrangement of reactance coils is the same,as though under. normal conditions the neutral wire were con-' nected to a point in the middle of the reactance connected between different points on the armature, while an increase of current between the neutral and either of the outside wires, for instance between the neutral to and outside wire 5, caused by. an unbalancing represented by lamps 17, moves the conncction of the neutral 16 away from the middle of the rcactance a distance proportional to the increase of current and in effect connects it to a point of variable and alternating voltags or to some segment of the commutator.

When the alternating voltage is superposed on the constant voltage of the neutral a pulsating voltage appears between the neutral 16 and outside wire 5, as shown in Figs. 4 and 5. The effective value of a pulsating voltage, as of an alternating voltage, is equal to the 33118111 root of the means or average square 0 the momentary voltages, and this is in excess of the average of the momentary voltages, and mayoonsequently be represented b the dotted line in Fi 5. In other words, t e effective value of the voltage between the neutral 16 and outside wire 5 is raised enough to compensate for the drop caused by the unbalancing. of the system.

My invention may be embodied in man other forms than that shown and describec and I therefore do not wish to be restricted to the exact form shown but intend to cover by the appended claims all changes and modi- [ications within the spirit and scope of my invention.

What I claim as new and desire to secure by [letters Patent of the United States, is:

l. The combination with a dynamo-else trir machine havin r an armature with a commutator connected to outside wires, a non tral wire, and automatic means for comoundin' the voltage between theneutral wire an rent in said neutral wire.

2. The combination with a dynamo-electric machine having an armature with .a

commutator connected to outside wires, of

means connected to said armature and re-* sponsive to current in a neutral wire for.

varying the effective voltage between either outside wire and said neutral wire.

3. The combination with a dynamo-electric machine havin an armature with a commutator connects to utside wires, of a variable reactance connected to diiierent. points on said armature and to a neutral wire and variable in response to current between either outside wire and the neutral wire to vary the effective voltage between said wires.

4. The combination with a dynamo-electrio machine having anarmature with a commutator connected to outside wires, of two reactance coils having diflerent characteristics connected to different points on sai an outside wire with varying curmature, and a neutral wire connected to a reactanee in response to ('hanges in current point between said coils. throu h the nails.

5. The combination with a dynaino-elve- 7. n a dynail'io-eleeti'iv machine the comtrie machine havin an armature with a roini bination with an armature having a rommumuta tor conneetejto outside wires, of two tat-or. of two reaetanee eoils connected in sereactance coils connected. from difl'erent ries between different points on the armalOliS being proportioned to change their reby a fraction of the current required to salum-tance unequally as the current in the neurate the core of the other coil.

tral changes. In witness whereof, I have hereunto set 6. In it dynuinmeleetrie n'uiehine the eomf my hand this 6th day oi'Jnnuax-y, 1908.

hination with an armature having a com- ERNST F. W. AlJ I-XANINCRSUN.

mutator, of two reaetnnee coils connected in Witnesses:

series between different points on the m'imt- BENJAMIN I3. Urn

ture and proportioned to vary unequally in HELEN ()nFolm points on the armature to a neutral, said 5 ture, one of said coils having u eore sulurntml' I 

